Continuous metal casting mold has been used for many years in the casting of metal sheets or slabs. A typical continuous-casting mold is a double-walled open-ended sleeve. The inner wall or the liner is usually formed of a high heat conductance material such as copper to furnish maximum thermal conductance. The outer wall or backing is usually formed of steel to furnish mechanical strength. Liquid metal is poured into the top of the mold and a partially solidified casting emerges continuously from the bottom of the mold. Cooling channels are formed between the backing and the liner through which water circulates to cool the liner and to help solidify the metal. The cooling channels can be machined into either the copper liner or the steel backing, but frequently into the steel backing to conserve copper material which is substantially more costly. The copper liner and the steel backing are fastened together by drilling and tapping holes in the outside surface of the copper liner and threading metal studs into these openings. The metal studs extend through mating openings in the backing plate and carry nuts which hold the copper plate and the steel plate securely in place. The conventional construction of a metal casting mold requires the use of a thick-walled copper liner to provide support for the studs which creates undesirable stress patterns.
U.S. Pat. No. 3,709,286 discloses a method for reducing the wall thickness of the copper liner by welding the studs to the copper liner either directly or through the use of intermediate metal strips. However, the construction of the mold proposed by the patent does not afford adjustability of the mold thickness or width and furthermore, does not provide a flexible mounting system between the copper liner and the steel backing so as to avoid thermal stress shock.
U.S. Pat. No. 3,964,727 discloses a continuous metal casting mold constructed of a pair of spaced apart mold plate members and a pair of mold side members to form an open-ended mold cavity for continuously casting metal there through. Even though the width of the mold can be adjusted to produce variable width metal castings, the patented device does not have any provisions to relieve the stress on the copper facing of the mold.
U.S. Pat. No. 4,635,702 discloses a mold for continuous casting of a steel strip that has two broad sidewalls opposing each other and are connected to two narrow walls arranged between the two sidewalls. The upper portion of the sidewalls defines a funnel-shaped casting area to accept molten metal. Since the broad sidewalls of the mold are of non-uniform thickness, there is a high likelihood that stress cracking problems caused by uneven thermal expansion in the sidewalls will occur. Moreover, the cost of such a thick-wall mold made of copper is very high and so is the maintenance cost of such a mold.
It is therefore an object of the present invention to provide an improved continuous metal casting mold that does not have the shortcomings of those prior art metal casting molds.
It is another object of the present invention to provide an improved continuous metal casting mold incorporating an insert and a mold frame from which the insert may be removed for service.
It is a further object of the present invention to provide an improved continuous metal casting mold that utilizes a thin, uniform-thickness copper facing plate fastened to a steel backing plate wherein the copper facing plate can be easily removed for service or replaced at relatively low cost.
It is another further object of the present invention to provide an improved continuous metal casting mold that utilizes an insert of a copper facing plate bolted to a steel backing plate in a floating arrangement such that the difference in thermal expansion between copper and steel can be compensated.
It is yet another object of the present invention to provide an improved continuous metal casting mold that utilizes a copper facing plate fastened to a steel backing plate in a flexible mounting arrangement such that it allows three dimensional movement of the copper plate in relation to the steel plate.
It is yet another further object of the present invention to provide an improved continuous metal casting mold that provides an expansion gap in the interface between the copper facing plate and the steel backing plate to allow for uneven expansion between copper and steel.
It is still another object of the present invention to provide an improved continuous metal casting mold that utilizes a thin copper facing plate which has uniform thickness to minimize thermal stresses and to maximize the wear life of the plate.